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iommu/arm-smmu: Work around MMU-500 prefetch errata

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MMU-500 erratum #841119 is tickled by a particular set of circumstances
interacting with the next-page prefetcher. Since said prefetcher is
quite dumb and actually detrimental to performance in some cases (by
causing unwanted TLB evictions for non-sequential access patterns), we
lose very little by turning it off, and what we gain is a guarantee that
the erratum is never hit.

As a bonus, the same workaround will also prevent erratum #826419 once
v7 short descriptor support is implemented.

CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Robin Murphy 2016-04-13 18:12:59 +01:00 committed by Will Deacon
parent e086d912d4
commit f0cfffc48c
2 changed files with 16 additions and 1 deletions
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1
Documentation/arm64/silicon-errata.txt
View File

@ -53,6 +53,7 @@ stable kernels.
| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
| ARM | Cortex-A57 | #852523 | N/A |
| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
| ARM | MMU-500 | #841119,#826419 | N/A |
| | | | |
| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |

16
drivers/iommu/arm-smmu.c
View File

@ -203,6 +203,7 @@
#define ARM_SMMU_CB(smmu, n) ((n) * (1 << (smmu)->pgshift))
#define ARM_SMMU_CB_SCTLR 0x0
#define ARM_SMMU_CB_ACTLR 0x4
#define ARM_SMMU_CB_RESUME 0x8
#define ARM_SMMU_CB_TTBCR2 0x10
#define ARM_SMMU_CB_TTBR0 0x20
@ -234,6 +235,8 @@
#define SCTLR_M (1 << 0)
#define SCTLR_EAE_SBOP (SCTLR_AFE | SCTLR_TRE)
#define ARM_MMU500_ACTLR_CPRE (1 << 1)
#define CB_PAR_F (1 << 0)
#define ATSR_ACTIVE (1 << 0)
@ -280,6 +283,7 @@ enum arm_smmu_arch_version {
enum arm_smmu_implementation {
GENERIC_SMMU,
ARM_MMU500,
CAVIUM_SMMUV2,
};
@ -1517,6 +1521,15 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
cb_base = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, i);
writel_relaxed(0, cb_base + ARM_SMMU_CB_SCTLR);
writel_relaxed(FSR_FAULT, cb_base + ARM_SMMU_CB_FSR);
/*
* Disable MMU-500's not-particularly-beneficial next-page
* prefetcher for the sake of errata #841119 and #826419.
*/
if (smmu->model == ARM_MMU500) {
reg = readl_relaxed(cb_base + ARM_SMMU_CB_ACTLR);
reg &= ~ARM_MMU500_ACTLR_CPRE;
writel_relaxed(reg, cb_base + ARM_SMMU_CB_ACTLR);
}
}
/* Invalidate the TLB, just in case */
@ -1762,6 +1775,7 @@ static struct arm_smmu_match_data name = { .version = ver, .model = imp }
ARM_SMMU_MATCH_DATA(smmu_generic_v1, ARM_SMMU_V1, GENERIC_SMMU);
ARM_SMMU_MATCH_DATA(smmu_generic_v2, ARM_SMMU_V2, GENERIC_SMMU);
ARM_SMMU_MATCH_DATA(arm_mmu500, ARM_SMMU_V2, ARM_MMU500);
ARM_SMMU_MATCH_DATA(cavium_smmuv2, ARM_SMMU_V2, CAVIUM_SMMUV2);
static const struct of_device_id arm_smmu_of_match[] = {
@ -1769,7 +1783,7 @@ static const struct of_device_id arm_smmu_of_match[] = {
{ .compatible = "arm,smmu-v2", .data = &smmu_generic_v2 },
{ .compatible = "arm,mmu-400", .data = &smmu_generic_v1 },
{ .compatible = "arm,mmu-401", .data = &smmu_generic_v1 },
{ .compatible = "arm,mmu-500", .data = &smmu_generic_v2 },
{ .compatible = "arm,mmu-500", .data = &arm_mmu500 },
{ .compatible = "cavium,smmu-v2", .data = &cavium_smmuv2 },
{ },
};